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                  <p class="p_Heading1"><span class="f_Heading1">Signal</span></p>



  
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                <p class="p_TextIndentedL2"><img src="d_signal.png" width="119" height="93" border="0" alt="d_signal"></p>
<p class="p_BodyText"><span class="f_BodyText">A </span><span class="f_BodyText" style="font-style: italic;">Signal</span><span class="f_BodyText"> is </span><span class="f_BodyText">a specification of </span><span class="f_BodyText" style="font-style: italic;"><a href="send.htm">Send</a></span><span class="f_BodyText"> request instances communicated between objects, typically in a </span><span class="f_BodyText"><a href="classdiagram.htm">Class</a> or <a href="packagediagram.htm">Package</a> diagram</span><span class="f_BodyText">. The receiving object handles the </span><span class="f_BodyText" style="font-style: italic;"><a href="receive.htm">Received</a></span><span class="f_BodyText"> request instances as specified by its </span><span class="f_BodyText" style="font-style: italic;">receptions</span><span class="f_BodyText">. The data carried by a Send request is represented as attributes of the Signal. A Signal is defined independently of the classifiers handling the signal occurrence.</span></p>
<p class="p_BodyText"><span class="f_BodyText">To define a reception, create an operation in the receiving object and assign the stereotype &lt;&lt;signal&gt;&gt; to it. The reception has the same name as the signal that the object can receive.</span></p>
<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">Toolbox Icon</span></p>
<p class="p_TextIndentedL2"><img src="e_signal.png" width="168" height="23" border="0" alt="e_signal"></p>
<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">OMG UML Specification</span></p>
<p class="p_BodyText"><span class="f_BodyText">The OMG UML specification (</span><span class="f_BodyText" style="font-style: italic;">UML Superstructure Specification, v2.1.1, p. 450</span><span class="f_BodyText">) states:</span></p>
<p class="p_OMGText"><span class="f_OMGText">A signal triggers a reaction in the receiver in an asynchronous way and without a reply. The sender of a signal will not block waiting for a reply but continue execution immediately. By declaring a reception associated to a given signal, a classifier specifies that its instances will be able to receive that signal, or a subtype thereof, and will respond to it with the designated behavior.</span></p>
<p class="p_BodyText"><span class="f_BodyText">And </span><span class="f_BodyText">(</span><span class="f_BodyText" style="font-style: italic;">UML Superstructure Specification, v2.1.1, p. 447 - 448</span><span class="f_BodyText">):</span></p>
<p class="p_OMGText"><span class="f_OMGText">A reception is a declaration stating that a classifier is prepared to react to the receipt of a signal. A reception designates a signal and specifies the expected behavioral response. The details of handling a signal are specified by the behavior associated with the reception or the classifier itself. ...Receptions are shown using the same notation as for operations with the keyword &lt;signal&gt;</span></p>




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